<template>
  <div class="s-canvas">
    <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
  </div>
</template>
<script setup>
import { nextTick } from 'vue'

var identifyCode={
  type: String,
  default: '1234'
}
//props
const props = defineProps({
  identifyCode: {
    type: String,
    default: '1234'
  },
  fontSizeMin: {
    type: Number,
    default: 28
  },
  fontSizeMax: {
    type: Number,
    default: 40
  },
  backgroundColorMin: {
    type: Number,
    default: 180
  },
  backgroundColorMax: {
    type: Number,
    default: 240
  },
  colorMin: {
    type: Number,
    default: 50
  },
  colorMax: {
    type: Number,
    default: 160
  },
  lineColorMin: {
    type: Number,
    default: 40
  },
  lineColorMax: {
    type: Number,
    default: 180
  },
  dotColorMin: {
    type: Number,
    default: 0
  },
  dotColorMax: {
    type: Number,
    default: 255
  },
  contentWidth: {
    type: Number,
    default: 112
  },
  contentHeight: {
    type: Number,
    default: 40
  }
})

//子组件通过 defineExpose 暴露出自身属性供父组件修改
defineExpose({
  setIdentifyCode(res){
    identifyCode= res
    drawPic()
  },
  getIdentifyCode(res){
    return identifyCode
  }
})

// 生成一个随机数
function randomNum (min, max) {
  return Math.floor(Math.random() * (max - min) + min)
}
// 生成一个随机的颜色
function randomColor (min, max) {
  var r = randomNum(min, max)
  var g = randomNum(min, max)
  var b = randomNum(min, max)
  return 'rgb(' + r + ',' + g + ',' + b + ')'
}
//等页面dom元素全都挂载后再执行后面的代码
async function drawPic () {
  await nextTick()
  var canvas = document.getElementById('s-canvas')
  var ctx = canvas.getContext('2d')
  ctx.textBaseline = 'bottom'
  // 绘制背景
  ctx.fillStyle = randomColor(
      props.backgroundColorMin,
      props.backgroundColorMax
  )
  ctx.fillRect(0, 0, props.contentWidth, props.contentHeight)
  // 绘制文字
  for (let i = 0; i < identifyCode.length; i++) {
    drawText(ctx, identifyCode[i], i)
  }
  drawLine(ctx)
  drawDot(ctx)
}
function drawText (ctx, txt, i) {
  ctx.fillStyle = randomColor(props.colorMin, props.colorMax)
  ctx.font = randomNum(props.fontSizeMin, props.fontSizeMax) + 'px SimHei'
  var x = (i + 1) * (props.contentWidth / (identifyCode.length + 1))
  var y = randomNum(props.fontSizeMax, props.contentHeight - 5)
  var deg = randomNum(-30, 30)
  // 修改坐标原点和旋转角度
  ctx.translate(x, y)
  ctx.rotate(deg * Math.PI / 270)
  ctx.fillText(txt, 0, 0)
  // 恢复坐标原点和旋转角度
  ctx.rotate(-deg * Math.PI / 270)
  ctx.translate(-x, -y)

}
function drawLine (ctx) {
  // 绘制干扰线
  for (let i = 0; i < 2; i++) {
    ctx.strokeStyle = randomColor(
        props.lineColorMin,
        props.lineColorMax
    )
    ctx.beginPath()
    ctx.moveTo(
        randomNum(0, props.contentWidth),
        randomNum(0, props.contentHeight)
    )
    ctx.lineTo(
        randomNum(0, props.contentWidth),
        randomNum(0, props.contentHeight)
    )
    ctx.stroke()
  }
}
function drawDot (ctx) {
  // 绘制干扰点
  for (let i = 0; i < 20; i++) {
    ctx.fillStyle = randomColor(0, 255)
    ctx.beginPath()
    ctx.arc(
        randomNum(0, props.contentWidth),
        randomNum(0, props.contentHeight),
        1,
        0,
        2 * Math.PI
    )
    ctx.fill()
  }
}
</script>
<style scoped>
.s-canvas {
  height: 38px;
  cursor: pointer;
}
.s-canvas canvas{
  margin-top: 1px;
  margin-left: 8px;
}
</style>
